About 8:20 p.m. Monday, a Dunkin’ Donuts store at 28 Winn St. in Burlington was held up. A man dressed in black and carrying a handgun entered the store, robbed it, and fled, Burlington police said.

About 20 minutes later, police responded to the Dunkin’ Donuts shop at 308 Great Road in Bedford for a report of an armed robbery. A masked man with a handgun crawled through the drive-up window and demanded money from the two employees there, Bedford police said.

“As the suspect walked over to the registers, the two employees were able to flee out the back door to a neighboring business,” said Bedford Police Chief Robert Bongiorno.

On surveillance video, the suspect is seen attempting to extract money from two cash registers, then fleeing, police said. When Bedford police arrived, they deployed a canine unit from Billerica, which lost track of the suspect about a block from the store.

Police did not say how much money the suspect took.

In the third robbery, police said a Dunkin’ Donuts store on Hingham Street in Rockland was held up at around 7:40 p.m. Tuesday. Police said the thief was wearing a blue hooded sweatshirt, black gloves, and a black mask and had a gun.

Bedford and Burlington police are working together to determine if those robberies are connected. Police believe a third robbery Monday night, at a Hess gas station in Waltham, might be connected and are coordinating with police there, Bongiorno said.

There are a number of similarities among all 22 Dunkin’ Donuts robberies, though police have officially connected only five. In every case, the suspect has brandished a gun or a knife, and he has frequently worn dark clothing.